Modern Design Concepts

Chapter 10

Second Half

Last Lecture of the Semester

Modern Airfoil Design

• NASA looked at developing an airfoil for general aviation that combine the high lift of the early 4-digit airfoils and the low drag of the 6- digit airfoils.– The key was the achievement of true laminar

flow over a significant portion of the airfoil strictly by the shape.

• No external blowing or artificial means of preserving the laminar boundary layer

Natural Laminar Flow Airfoils

• These new airfoils were called natural laminar flow airfoils

• The old NACA airfoils could only be altered one parameter at a time

• The new approach that NASA used was to first specify the desired characteristics that a particular airfoil required; then design it to meet those requirements. – This was called the inverse design.

NASA

• NASA worked with the Eppler method which began with a prescribed pressure disturbance over the airfoil, and applied various aerodynamic theories to analyze the flow and establish the boundary layer characteristics

Eppler Method

• The Eppler method had provisions to account for altitude at gross weight.

• This method allowed NASA to account for a variety of considerations

First Airfoil Intended for Light Single Engine Airplanes

• The first airfoil intended for light single engine airplanes was the NASA NFL (1)-0416.– The fist two numbers(04) signify a design lift

coefficient of 0.4 and the 16 refers to a maximum thickness of 16% of the chord.

– The 1 in parenthesis refers to the first generation of such airfoils

Newer Design Details

• Swept vertical Fins & T-tail arrangements

• Winglets, improved cowl shapes, carefully designed fillets

• *** All these aerodynamic refinements are quite beneficial

Potential Airliner Designs

• Engine Efficiency/Aerodynamic efficiency– higher aspect ratios

• Very Narrow Chord Wings– reducing skin friction drag, increasing

favorable pressure gradient; increasing laminar flow at higher speeds

• Span Loading– distributing the payload over all of the span

Potential General Aviation Designs

• Composite structures– can be molded & bound for very smooth

aerodynamic surfaces– boron or carbon fibers give high strength with

little weight– composites smoother & stronger

Potential General Aviation Designs

• Development in Propulsion systems

• Rotary/Wankel engine– an internal combustion engine without pistons– the combustion process drives the rotor in

continuous, smooth, rotating manner– can run on a variety of fuels– it does not produce a tremendous amount of

power for its weight

Potential General Aviation Designs

• Development in Propulsion systems

• Turboprops– prime performance for business & commuter

planes– single and multi engine– pictures on pages 295-298

Quiz on Chapter 10

Take out a sheet of paper

Include today’s date and your name

Quiz on Chapter 10

• How has the study of aerodynamics affected modern aircraft design? Support your answer with an example.